JPS6049249B2 - gas analysis system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas analysis system in which a sample gas sampled by a probe is introduced into a gas analyzer through a semipermeable membrane gas phase dehumidifier.

Generally, if the sample gas introduced into the gas analyzer contains moisture, the window of the reaction cell will be contaminated or span drift will occur, so it is desirable to remove as much moisture as possible from the sample gas.

Among gas analyzers, especially in the case of a 502 gas analyzer, 502 gas easily dissolves in drain, so the moisture in the sample gas is removed using a dehumidifier, and the sample gas is removed from the probe that collects the sample gas to the dehumidifier. All gas conduits are heated to above the dew point of the 500 gas.
However, when the distance between the probe and the dehumidifier increases,
Power consumption for heating the conduit increases and it becomes difficult to provide uniform heating. In order for a gas analyzer to operate accurately and stably for a long period of time, dust, mist, and moisture must be pretreated to a clean state with minimal loss of sample gas before introduction into the analyzer. No. However, in order to reduce losses during pretreatment, it is necessary to reduce the amount of condensed water as much as possible, reduce the contact time between the condensed water and the sample gas, and use materials that do not react with the components to be analyzed as materials in contact with the sample gas. Consideration must be given to the selection of materials.

In order for the semipermeable membrane vapor phase dehumidifier to operate well, it is necessary to remove dust, mist, and moisture in advance.

Furthermore, if instrument air is not available as the dry charge gas for the vapor phase dehumidifier, it must be produced by the system itself. An object of the present invention is to provide a gas analysis system equipped with an inexpensive and efficient sample gas dehumidifying means that reduces the complexity of maintenance and inspection as much as possible.

A further object of the present invention is to provide a gas analysis system that can prevent freezing accidents at the drain outlet in cold regions and does not require heating or keeping warm of the gas pipe between the probe and the dehumidifier. It is.

To achieve this object, the present invention provides, in the gas analysis system mentioned at the beginning, an atmosphere-opening tube with one end open to the atmosphere, and the gas discharged from the gas analyzer being exhausted into the atmosphere-opening tube. This gas analysis system is characterized in that the exhausted exhaust gas is introduced into a vapor phase dehumidifier as a dry charge gas.

The present invention will be further described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. The sample gas is sampled by a probe 1, where coarse dust is removed and then passed through a filter 2 provided as required.
to go into. Condensed water generated on the filter 2 when the sample gas contains water is sucked together with the bypass gas by the first air aspirator 12. Here, when the filter 2 and the dehumidifier 3, which will be described later, are housed in a constant temperature bath 30 heated to a temperature higher than the dew point temperature of the sample gas, the above-mentioned condensed water is not generated, and gas dissolution loss can be reduced.
In addition, by bypassing a part of the sample gas from the filter 2 and sucking it with the air espirator 12,
Since a larger amount of sample gas is sucked into the filter 2 per unit time, the rate at which the sample gas in the filter 2 is replaced with new sample gas becomes faster, and the inside of the filter is sucked from near the filter base and outer surface. By bypassing the sample gas sucked into the filter, it is possible to avoid a situation where old sample gas accumulates in the filter. The first air espirator 12 does not require a large suction force, and is preferably constructed so that the suction force does not change even if dust or drainage is mixed in. The condensed water sucked in by this is diluted with air and discharged in a state close to a gas phase, so there is no fear that the discharge port will freeze and become clogged. The sample gas that has passed through the filter 2 is dehumidified by a semi-permeable membrane gas phase dehumidifier 3 until the outlet gas dew point becomes below the outside air temperature, and is further introduced into a gas analyzer 7 through a pump filter 5 and a flow meter 6. be done. Particularly in certain types of analyzers, such as infrared analyzers, reading errors occur when the sample gas pressure within the analyzer changes.To reduce this, one end of the gas outlet of analyzer 7 is opened to the atmosphere. It is connected to the atmosphere opening pipe 8 through a conduit 21.

The atmosphere release pipe 8 branches from there and further includes a flow meter 9 and a needle valve 10 for making the purge gas of the gas phase dehumidifier 3 negative pressure.
through the purge side of the vapor phase dehumidifier 3 to the second air respirator 13 . conduit 22
A pressure gauge 11 is also provided. The second air espirator 13 is made to generate a high vacuum. Both air aspirators 12, 13 perform the intended suction action with the aid of compressed air.

FIG. 2 shows the detailed structure of the atmosphere opening pipe 8. As shown in FIG.

The sample gas discharged from the gas analyzer 7 through the conduit 21 is exhausted to an inlet 82 on the opposite side of the open end 81 of the atmosphere-opening tube 8 . The dry sample gas exhausted into the atmosphere open tube 8 is guided from the outlet 83 through the purge gas intake conduit 22 to the flow meter 9. The reason for passing it through the open tube 8 will be explained in more detail.

As mentioned above, an infrared analyzer is often used as the analyzer 7.

This infrared analyzer utilizes the fact that molecules with a dipole moment absorb infrared rays at a wavelength unique to each molecule, creating a transition between vibrational energy levels. The concentration can be measured by guiding the sample gas and measuring the attenuation rate of the infrared rays transmitted through the measurement cell at a wavelength that is absorbed by the molecules whose concentration in the sample gas is to be measured. For this reason, if the gas pressure in the measuring cell is doubled, for example, the molecular density therein also doubles, and as a result the concentration measurement value also doubles.

Therefore, in order to perform accurate concentration measurements, it is necessary to maintain the gas pressure within the measurement cell constant.

However, when the analyzer 7 is directly connected to the gas phase dehumidifier 3 in order to obtain the purge gas for the gas phase dehumidifier 3 from the gas analyzer 7, the gas pressure in the measurement cell of the analyzer 7 is It may fluctuate, and accurate concentration measurements cannot be expected. Therefore, by using the atmosphere opening tube 8, the gas pressure within the measurement cell is maintained at a constant pressure of approximately atmospheric pressure, thereby ensuring the accuracy of the concentration measurement in the analyzer 7.

FIG. 3 shows the detailed structure of the semipermeable membrane type gas phase dehumidifier 3.

This vapor phase dehumidifier 3 has partition plates 32 and 3 inside an outer tube 31.
A plurality of inner tubes 34 are supported through three tubes.
Each inner tube 34 is made of, for example, N.AF'ION, a product of DuPont, and has a function of selectively transmitting water vapor. Therefore, a sample gas containing water vapor, that is, a wet sample gas, is introduced into each inner tube 34 from the inlet 35 and
In the process, water vapor in the sample gas is discharged into the outer tube 31 through the tube wall of each inner tube 34.
On the other hand, if the dry purge gas led from the atmosphere open tube 8 is allowed to flow from the purge gas inlet 37 of the outer tube 31 toward the outlet 38, the water vapor in the sample gas discharged into the outer tube 31 will be introduced from the inlet 37. The wet purge gas is absorbed into the dry purge gas inlet and taken out as wet purge gas discharged from the outlet 38. In this way, a dry sample gas containing no water vapor can be obtained from the outlet 36. FIG. 4 shows a capillary type fixed crest 1 in place of the needle valve 10 in FIG.
This figure shows an example in which 4 is arranged.

According to this configuration, the purge side pressure of the dehumidifier 3 can be determined from the indication of the flow meter 9 by utilizing the fact that the flow rate and the differential pressure between both ends of the fixed crest 14 are almost proportional. The pressure gauge 11 in FIG. 1 can be omitted. Figure 5 shows
By inserting the capillary fixed ridge 15 on the side of the filter 2, which has weak suction power, it can be used commonly for suctioning wet purge gas from the vapor phase dehumidifier 3, and for suctioning condensed water and bypass gas from the filter 2. air respirator 16
This section shows an example in which this can be done.

As described above, according to the present invention, by providing the air release pipe on the outlet side of the gas analyzer, dry exhaust gas from the analyzer can be removed from the dry chamber for the dehumidifier without affecting the instructions of the analyzer. It can be used effectively as a gas, and by using a highly durable air espirator that has no moving or consumable parts at the dry-burge gas inlet of a dehumidifier, it is possible to periodically replace the diaphragm valve in a diaphragm-type suction device, for example. It is possible to create a so-called maintenance-free system that does not require such complicated work and requires almost no maintenance or inspection.

Furthermore, by providing a dehumidifier immediately after the probe, no condensed water is generated within the analytical instrument panel, so there is no need for a special dehumidifier within the panel. The dehumidifying capacity of a semipermeable membrane vapor phase dehumidifier depends on its ambient temperature; as the ambient temperature decreases, the dehumidifying capacity increases and the outlet gas dew point decreases.

Therefore, it is necessary to expose the sample gas outlet side of the dehumidifier 3 to the outside air temperature, whereby the outlet gas dew point slides up and down with the outside air temperature, achieving the purpose of eliminating the need for gas conduit heating. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a system diagram of one embodiment of the present invention, Figure 2 is a vertical sectional view showing details of the atmosphere opening pipe in Figure 1, and Figure 3 is the semipermeable membrane type shown in Figure 1. A vertical sectional view showing details of the vapor phase dehumidifier, and FIGS. 4 and 5 are system diagrams of essential parts showing other embodiments of the present invention, respectively.

1... Probe, 3... Semi-permeable membrane gas phase dehumidifier, 4... Pump, 6, 9... Flow meter, 7... ... Gas analyzer, 8 ... Air release pipe, 10 ... Needle valve, 11 ... Pressure gauge, 12, 13, 16 ... Air S 5 pirator , 14... Capillary type fixed aperture.

Claims (1)

[Claims] 1. In a gas analysis system in which a sample gas sampled by a probe is introduced into a gas analyzer through a semipermeable membrane gas phase dehumidifier, an atmosphere-opening pipe with one end open to the atmosphere is provided. A gas analysis system characterized in that the gas discharged from the gas analyzer is discharged into the atmosphere open pipe, and the discharged exhaust gas is introduced into the vapor phase dehumidifier as dry purge gas. 2. In the gas analysis system according to claim 1, a flow meter, a Nield valve, and a pressure gauge are arranged in the conduit between the atmosphere release pipe and the dry purge gas inlet of the vapor phase dehumidifier. An analysis system characterized by: 3. In the gas analysis system according to claim 1, a flow meter and a capillary fixed ridge are arranged in the conduit between the atmosphere open pipe and the dry purge gas inlet of the vapor phase dehumidifier. A gas analysis system characterized by: